1. Field of the Invention
The present invention relates to a numerical controller having a tool posture control function for multi-axis machining machines, for controlling a multi-axis machining machine that has at least three linear axes and at least three rotation axes including one rotation axis for tool phase control.
2. Description of the Related Art
In a multi-axis machining machine that has at least three linear axes and at least three rotation axes including one rotation axis for tool phase control, a workpiece may be machined, as described in [1] to [3] below, while a tool center point position, a tool direction and a tool phase direction are caused to vary.
[1] Fiber Placement Machine
A fiber placement machine is a processing machine in which a fiber (carbon fiber reinforced plastic material) paid out of a roller is wound around a workpiece that has a smooth surface, for instance aircraft fuselage, wings and rocket bodies. A tool position (arm position) is controlled by an arm that operates in the X, Y, Z-axes. The tool direction is controlled in two rotation axes, i.e. B-axis and C-axis. The tool phase direction (roller direction) is controlled in a further rotation axis, i.e. A-axis.
In FIG. 1, the main body of the fiber placement machine is present on the right side, but is not depicted in the picture. The workpiece is drawn relatively small with respect to the tool. As illustrated in FIG. 2, the fiber is wound while the tool center point position moves smoothly over the workpiece and while the tool direction and the tool phase direction are caused to vary smoothly. In FIG. 2, the pathway where the tool center point position changes is drawn as tool center point pathway and the pathways where the vector tips that denote the tool direction and the tool phase direction change are respectively drawn as the tool direction pathway and the tool phase direction pathway. The vector that denotes the tool direction and the tool phase direction is set to a unit vector. The same applies hereafter.
[2] Water Jet Machine
Herein, a water jet machine is a processing machine that cuts a workpiece through jetting of high-pressure cutting water out of a nozzle, as illustrated in FIG. 3. A catcher that receives cutting water is supported by an arm. The tool position (tool head position) is controlled in three linear axes, namely the X-axis, Y-axis and Z-axis, the tool direction (nozzle direction) is controlled in two rotation axes, namely the B-axis and C-axis, and the tool phase direction (arm direction) is controlled in one further rotation axis, namely the A-axis.
As illustrated in FIG. 4, the workpiece is cut while the tool center point position moves smoothly over the workpiece and while the tool direction (nozzle direction) and the tool phase direction (arm direction) are caused to vary smoothly.
[3] Hale Machining
Hale machining is a kind of machining where a haling tool (non-rotational tool) is used and wherein the tool posture is controlled in such a manner that the tool direction is substantially perpendicular to the machined surface of the workpiece, and the rake face of the tool is substantially perpendicular to the tool center point pathway, as illustrated in FIG. 5. The tool position (tool head position) is controlled in three linear axes, namely the X-axis, Y-axis and Z-axis, the tool direction is controlled in two rotation axes, namely the B-axis and C-axis, and the tool phase direction is controlled in one further rotation axis, namely the A-axis.
As illustrated in FIG. 6, the workpiece is machined while the tool center point position moves smoothly over the workpiece and while causing the tool direction and the tool phase direction to vary smoothly.
In the explanation of the above-described multi-axis machining machines, the tool direction is controlled in the B-axis and C-axis, and the tool phase direction is controlled in the A-axis, but other examples are possible wherein the tool direction is controlled in the A-axis and B-axis, and the tool phase direction is controlled in the C-axis; or, alternatively, the tool direction is controlled in the A-axis and C-axis, and the tool phase direction is controlled in the B-axis. The examples of the above multi-axis machining machines involve a multi-axis machining machine of tool head rotation type, wherein the rotation axes in which the tool direction and the tool phase direction are controlled are on the tool side, but may involve a multi-axis machining machine of table rotation type in which a rotation axis or rotation axes are on a table side and a table and a tool are caused to rotate relatively to each other (see FIG. 21 in which tool direction is controlled in the B-axis and C-axis, while tool phase direction is controlled in the A-axis), or a mixed-type multi-axis machining machine in which a rotation axis or rotation axes are both on the tool side and the table side and the table and the tool are caused to rotate relatively to each other (see FIG. 22 in which tool direction is controlled in the A-axis and C-axis, while tool phase direction is controlled in the B-axis).
Japanese Patent Application Laid-Open No. 2009-301232 discloses a numerical controller for tool phase control where coordinate transformation (inclined-plane machining instruction) can be performed for a tool center point control instruction, including control of the roller direction (tool phase direction) in a third rotation axis. However, the numerical controller for tool phase control controls only the tool phase direction, and does not involve the technical idea of interpolating smoothly the tool center point position and tool posture (tool direction and tool phase direction).
Japanese Patent Application Laid-Open No. 2005-182437 discloses a numerical controller in which interpolation is performed using a smooth curve that approximates an expected curve, even in four- or five-axis processing machines such as those where a workpiece is machined with a tilted tool. In this numerical controller, a correction vector end point that corresponds to an instruction vector is worked out by displacing the vector endpoint of the instruction vector towards a position that is closest to an approximation curve for the vector end point, within a set tolerance range, in order to smoothly vary the working point and the relative relationship between the tool and the workpiece. Specifically, this patent document discloses the feature of correcting an instruction vector that denotes a tool direction, to yield a smooth curve, but does not disclose the technical idea of smoothly interpolating a tool center point position and a tool posture (tool direction and tool phase direction) including a tool phase direction. Accordingly, the above technology cannot be used in a machine tool that requires control of the tool phase direction.
Japanese Patent Application Laid-Open No. 2007-322392 discloses a posture smoothing method that allows obtaining a time series of posture information in which offset is removed from a time series of posture information which includes offset of an object, on an image captured by imaging means. This posture smoothing method is a technology relating to image processing, but not a technology for controlling machine tools. That is, the above patent document does not disclose the technical idea of interpolating smoothly the tool center point position and tool posture (tool direction and tool phase direction), or the technical idea of controlling three linear axes and three rotation axes on the basis of the tool center point position and tool posture.
Japanese Patent Application Laid-Open No. H5-324047 discloses a tangential direction control scheme of tool axes that enables control in such a manner that the tool faces constantly a tangential direction with respect to the travel direction. Herein, performing control in such a manner that a tool faces constantly a tangential direction with respect to the travel direction is found to be equivalent to controlling the tool phase. However, the above patent document does not disclose the technical idea of interpolating smoothly the tool center point position and tool posture (tool direction and tool phase direction).